Treatment of circulating water systems

ABSTRACT

The present invention relates to a method of inhibiting the growth of killing algae, bacteria, yeast and/or fungi in a recirculating water system which comprises adding to the water a polymeric biguanide and an adjuvant of the Formula (1) or a salt thereof:                    
     wherein: 
     R 1  is an optionally substituted C 8  to C 12  or C 18  to C 22  alkyl group; and 
     R 2  and R 3  each independently is H or optionally substituted C 1-4 -alkyl.

This application claims the benefit of Provisional application No.60/209,230 filed Jun. 2, 2000.

FIELD OF INVENTION

This invention relates to a method for inhibiting the growth of orkilling microorganisms such as algae, bacteria, yeast and/or fungi in arecirculating water system, to treated recirculating water systems andto compositions and kits suitable for use in the method.

BACKGROUND OF THE INVENTION

The water in many industrial and recreational recirculating watersystems such as cooling towers, swimming pools, spas, ornamental ponds,plumbing, pipework and other surfaces and the like is susceptible toinfection by microorganisms such as bacteria, algae, yeast and fungi.These organisms may be pathogens or potential pathogens. Thus, forsafety reasons, it is highly desirable to control their growth by theaddition to the water of sanitizing agents. It is also desirable foraesthetic reasons, to control the growth of non-pathogenic bacteria,algae, yeast and fungi, particularly the so-called “nuisance” algae,yeast and fungi which cause discoloration and/or staining of the waterand surfaces in contact with the water

A variety of sanitising agents have been employed for controllingundesirable micro-organisms in recreational recirculating water systems.The most common sanitising agents provide free chlorine and/or bromine(typically at a concentration in the water of 1 to 5 ppm free halogen).Chlorine may be provided either directly as chlorine gas or sodium orcalcium hypochlorite or via a chlorine release agent such as achlorinated isocyanurate or chlorinated and brominated hydantoin.Chlorine may also liberated in situ by electrolysis of sodium chloride.Other sanitising agents which have been used in such systems includeozone, ozone forming chemicals, hydrogen peroxide, hydrogen peroxideforming chemicals, copper and/or silver salts which provide copper,silver or chelated copper ions (typically at a concentration in thewater of 0.1 to 1.0 ppm), quaternary amines and polymeric biguanides,especially poly(hexamethylene biguanide) (hereinafter referred to asPHMB) which is typically used at a concentration in recreational waterof 6-10 ppm. Systems employing ultra violet light have also been used tosanitise recirculating water. Sanitising agents are used at higherconcentrations in industrial recirculating water systems and additionalsanitising agents may be used including but not limited to2-methylisothiazolinone, 5-chloro-2-methylisothiazolinone,benzisothiazolinone, 2-bromo-2-nitropropane-1,3-diol,1,2-dibromo-2,4-dicyanobutane, methylene bisthiocyanate,2-(thiocyanomethylthio)-benzothiazole, formaldehyde and formaldehyderelease agents, glutaraldehyde, dibromonitrilopropionamide andbromo-hydroxyacetophenone or mixtures thereof.

Although these primary sanitising agents are very effective incontrolling bacteria they do not always provide consistent control ofthe so called “nuisance” algae, yeast and fungi which can causediscoloration and/or staining of the water and surfaces in contact withthe water.

Examples of “nuisance” algae which are found in swimming pools includeeukaryotic and prokaryotic algae, for example green algae (e.g.Chlorella spp.), black algae (e.g. Phormidium spp.) and mustard algae(e.g. Eustigmatos spp.). Of these, we have found that mustard algae areparticularly difficult to control, regardless of the type of primarysanitising agent used. They appear as slimy deposits attached to thepool sides and bottom, as well as in the plumbing and in the filter, andvary in colour from dark green to brown.

Examples of “nuisance” fungi (often referred to as mold) isolated fromswimming pools include Aspergillus spp., Cladosporium spp., Mucor spp.and Paecilomyces spp. Paecilomyces lilacinus is the causative agent inso-called “water mold”, “pink mold” and “pink algae”. P lilacinus canmanifest itself as white, grey or pink slimy deposits that are found inniches such as under ladder steps, in skimmer and pump baskets, infilters and piping. P lilacinus is also found growing in recirculatingwater filters where it can have an adverse effect on the efficiency andlifespan of the filter media. In its mature form, the fungus can alsoattach itself to pool surfaces and cause chronic turbidity problemswhich are difficult to control.

Examples of common “nuisance” yeasts found in swimming pools includeSaccharomyces and Candidia species.

The wide spread occurrence of “nuisance” algae and fungi has lead to theintroduction of methods of controlling these persistent microbes such asdosing with larger amounts of the sanitiser, shock dosing with chlorineor the introduction of further sanitisers or additives such as chelatedcopper, copper sulfate, combinations of chlorine and ammonium sulfate,colloidal silver, linear and/or cyclic quaternary amine compounds andpolyquaternary amine compounds. However, these methods andalgicides/fungicides have shown only limited efficacy against the“nuisance” algae and fungi and can give rise to undesirable levels offoam, especially in re-circulating water systems such as spas.Furthermore, in some circumstances, the additives themselves (especiallychelated copper and copper sulphate) can cause staining of surfaces incontact with the water.

Any agent to be added to a recreational water system to controlbacterial growth and “nuisance” algae, yeast and fungi must meet anumber of demanding performance criteria. These include:

a) an excellent toxicology profile;

b) reasonable solubility;

c) freedom from unpleasant taste;

d) odourless or free from unpleasant odours (post addition);

e) non-staining of the construction materials e.g. plaster, plastic;

f) stability to light;

g) stability to other additives present in the water (e.g. sanitisers,H₂O₂ and EDTA);

h) little or no effect on foaming; and

i) no adverse effect on water appearance e.g. discoloration orturbidity.

Thus, there is a need for a method of treating recirculating watersystems to control not only the growth of pathogens, potential pathogensand other bacteria, but also the growth of those “nuisance” algae, yeastand/or fungi which persist in the presence of a primary sanitizingagent.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method forinhibiting the growth of or killing microorganisms, particularlybacteria, algae, yeast, and/or fungi in a recirculating water systemcomprising adding to the water a polymeric biguanide and an adjuvant ofthe Formula (1) or a salt thereof:

wherein:

R¹ is an optionally substituted C₈ to C₁₂ or C₁₈ to C₂₂ alkyl group; and

R² and R³ each independently is H or optionally substituted C₁₋₄-alkyl.

The Adjuvant

The alkyl group represented by R¹ may be a branched chain or morepreferably a straight chain alkyl group. It is especially preferred thatR¹ is n-octadecyl or more preferably n-dodecyl.

When any of R² and R³ is C₁₋₄-alkyl it may be a branched chain or morepreferably a straight chain alkyl group. Examples of suitable alkylgroups include ethyl, n-propyl, iso-propyl and especially methyl. It ispreferred however that R² and R³ are H.

The alkyl groups represented by R¹, R² and R³ may be substituted by oneor more substituents which do not adversely affect the activity of theadjuvant when used in combination with a polymeric biguanide accordingto the present invention. Suitable optional substituents includehydroxy, aryl (especially phenyl), amino, C₁₋₄-alkoxy,hydroxy-C₁₋₄-alkoxy or halogen (especially Cl). It is preferred, howeverthat R¹, R² and R³ are un-substituted.

The adjuvant is preferably sufficiently water-soluble to give aconcentration thereof in the recirculating water system which issufficient to inhibit the growth of or kill microorganisms such asbacteria, algae, yeast, and/or fungi present in the recirculating watersystem. When the adjuvant is added to a recreational recirculating watersystem such as a swimming pool or spa it is also preferable that theadjuvant has sufficient water solubility not to adversely effect theappearance of the water in the recirculating water system, for examplewater colour or clarity.

Preferably the adjuvant has a water-solubility of at least 1 ppm,preferably at least 2 ppm, especially at least 5 ppm more especially atleast 50 ppm and particularly at least 100 ppm. The upper limit of theadjuvant's water-solubility does not matter, although typically theadjuvant has a water-solubility below 100,000 ppm, more usually below25,000 ppm.

The term “ppm” means parts per million by weight. One may easilydetermine the water-solubility of an adjuvant in ppm because this is thesame as the weight of adjuvant in milligrams which will dissolve in 1liter of water at 20° C. For example if 10 mg of adjuvant dissolves in 1liter of water at 20° C. the water-solubility is 10 ppm.

The solubility of many adjuvants is influenced by pH. In a recreationalrecirculating water system the pH is preferably in the range of from 6.5to 9.0, more preferably from 6.8 to 8.5 and especially from 7.0 to 8.2.Accordingly the above mentioned preferred solubility of the adjuvant isthe solubility in water at the pH of the recirculating water system.

The adjuvant is preferably added to the water system to give aconcentration thereof in the range 0.1 to 30 ppm, more preferably 0.1 to24 ppm, more preferably 0.5 to 15 ppm, especially 5 to 15 ppm and moreespecially 6 to 10 ppm. These preferred concentrations provide goodprotection against the growth of microorganisms such as bacteria andnuisance algae, yeasts and fungi. It is especially preferred that theconcentration of adjuvant is less than 25 ppm, because we have foundthat in some circumstances a higher concentration of adjuvant can resultin water turbidity.

In view of the foregoing preferences the adjuvant is preferably selectedfrom the group consisting of dodecylamine, octadecylamine,N,N-dimethyloctadecylamine and salts thereof. It is especially preferredthat the adjuvant is dodecylamine or octadecylamine or a salt thereof.More especially the adjuvant is dodecylamine or a salt thereof.Dodecylamine provides good protection against the growth ofmicroorganisms such as bacteria and “nuisance” algae, yeast and/or fungiand does not affect water quality, particularly water clarity.

When the adjuvant is used in the form of a salt, the salt may be formedwith any anion which does not adversely affect the activity of theadjuvant when used with the polymeric biguanide. Preferably, the salt isan acid addition salt, more preferably a water-soluble acid additionsalt. The acid forming the salt may be an inorganic acid or an organicacid. When the acid is an inorganic acid it is preferably hydrochloricacid.

When the salt is formed with an organic acid, the acid may contain aphosphonic, phosphoric, sulphonic or sulphate group but preferablycontains a carboxylic acid group. The organic acid may be aromatic butis preferably aliphatic, including alicyclic. When the organic acid isaliphatic, the aliphatic chain of the organic acid may be linear orbranched, saturated or unsaturated, including mixtures thereof.Preferably, the aliphatic chain is linear and it is also preferred thatthe organic acid is an aliphatic carboxylic acid.

It is preferred that the organic acid contains up to 12, more preferablyup to 6 carbon atoms excluding the acid group.

The organic acid may contain more than one acid group but it ispreferred that only one such group is present.

The organic acid may be substituted by a halogen or particularly ahydroxy group.

Suitable aliphatic carboxylic acids from which the salt can be formedinclude acetic acid, propionic acid, butyric acid, valeric acid, pivalicacid and lauric acid. Suitable aliphatic di-carboxylic acids includeoxalic acid, malonic acid, succininic acid and gluconic acid. Suitablehydroxy substituted acids include glycolic acid, lactic acid, glycericacid, malic acid and tartaric acid.

The salts of the adjuvant may be formed using conventional methods, forexample by reacting the compound of Formula (1) with the acid optionallyin the presence of a solvent. The resulting salt may then be isolatedby, for example evaporation. It is preferred that the resulting salt ispurified prior to use in the present method to remove undesirableimpurities.

A single adjuvant or two or more of the adjuvants may be used in thepresent method. The use of two or more of the adjuvants mayadvantageously provide a broader spectrum of activity than the use of asingle adjuvant.

Polymeric Biguanide

The polymeric biguanide preferably contains at least two biguanide unitsof Formula (2):

linked by a bridging group which contains at least one methylene group.The bridging group preferably includes a polymethylene chain, optionallyincorporating or substituted by one or more hetero atoms such as oxygen,sulphur or nitrogen. The bridging group may include one or more cyclicmoieties which may be saturated or unsaturated. Preferably, the bridginggroup is such that there are at least three, and especially at leastfour, carbon atoms directly interposed between two adjacent biguanideunits of Formula (2). Preferably, there are not greater than 10 andespecially not greater than eight carbon atoms interposed between twoadjacent biguanide units of Formula (2).

The polymeric biguanide may be terminated by any suitable group, such asa hydrocarbyl, substituted hydrocarbyl or by an amine group or by acyanoguanidine group of the formula:

When the terminating group is hydrocarbyl, it is preferably alkyl,cycloalkyl, aryl or aralkyl. When the terminating group is substitutedhydrocarbyl, the substituent may be any substituent which does notexhibit undesirable adverse effects on the microbiological properties ofthe polymeric biguanide. Preferred aryl groups include phenyl groups.Examples of suitable substituents are aryloxy, alkoxy, acyl, acyloxy,halogen and nitrile.

When the polymeric biguanide contains two biguanide groups of Formula(2), it is preferred that the two biguanide groups are linked through apolymethylene group, especially a hexamethylene group and the biguanideis a bisbiguanide.

The terminating groups in such bisbiguanides are preferably C₁₋₁₀-alkylwhich may be linear or branched and optionally substituted aryl,especially optionally substituted phenyl. Examples of such terminatinggroups are 2-ethylhexyl and 4-chlorophenyl. Specific examples of suchbisbiguanides are compounds represented by Formula (3) and (4) in thefree base form:

The polymeric biguanide preferably contains more than two biguanideunits of Formula (2) and is preferably a linear polymeric biguanidewhich has a recurring polymeric chain represented by Formula (5) or asalt thereof:

wherein X and Y represent bridging groups which may be the same ordifferent and in which together the total of the number of carbon atomsdirectly interposed between the pairs of nitrogen atoms linked by X plusthe number of carbon atoms directly interposed between the pairs ofnitrogen atoms linked by Y is more than 9 and less than 17.

The bridging groups X and Y preferably consist of polymethylene chains,optionally interrupted by hetero atoms, for example, oxygen, sulphur ornitrogen. X and Y may also incorporate cyclic moieties which may besaturated or unsaturated, in which case the number of carbon atomsdirectly interposed between the pairs of nitrogen atoms linked by X andY is taken as including that segment of the cyclic group, or groups,which is the shortest. Thus, the number of carbon atoms directlyinterposed between the nitrogen atoms in the group

is 4 and not 8.

The linear polymeric biguanides having a recurring polymer unit ofFormula (5) are typically obtained as mixtures of polymers in which thepolymer chains are of different lengths. Preferably, the number ofindividual biguanide units of formulae:

is, together, from 3 to about 80.

The preferred linear polymeric biguanide is a mixture of polymer chainsin which X and Y are identical and the individual polymer chains,excluding the terminating groups, are of the Formula (6) or a saltthereof:

wherein n is from 4 to 40 and especially from 4 to 15. It is especiallypreferred that the average value of n is about 12. Preferably, theaverage molecular weight of the polymer in the free base form is from1100 to 3300.

The linear polymeric biguanides may be prepared by the reaction of abisdicyandiamide having the formula:

with a diamine H₂N—Y—NH₂, wherein X and Y have the meanings definedabove or by reaction between a diamine salt or dicyanimide having theformula:

with a diamine H₂N—Y—NH₂ wherein X and Y have the meanings definedabove. These methods of preparation are described in UK specificationsnumbers 702,268 and 1,152,243 respectively, and any of the polymericbiguanides described therein may be used.

As noted hereinbefore, the polymer chains of the linear polymericbiguanides may be terminated either by an amino group or by acyanoguanidine group:

This cyanoguanidine group can hydrolyse during preparation of the linearpolymeric biguanide yielding a guanidine end group. The terminatinggroups may be the same or different on each polymer chain.

A small proportion of a primary amine R—NH₂, where R represents an alkylgroup containing from 1 to 18 carbon atoms, may be included with thediamine H₂N—Y—NH₂ in the preparation of polymeric biguanides asdescribed above. The primary amine acts as a chain-terminating agent andconsequently one or both ends of the polymeric biguanide polymer chainsmay be terminated by an —NHR group. These —NHR chain-terminatedpolymeric biguanides may also be used.

The polymeric biguanides readily form salts with both inorganic andorganic acids. Preferred salts of the polymeric biguanide arewater-soluble. When the polymeric biguanide is represented by a compoundof Formula (3) in the free base form, a preferred water soluble salt isthe digluconate. When the polymeric biguanide is represented by acompound of Formula (4) in the free base form, a preferred water solublesalt is the diacetate. When the polymeric biguanide is a mixture oflinear polymers represented by Formula (6) in the free base form, thepreferred salt is the hydrochloride.

It is especially preferred that the polymeric biguanide is a mixture oflinear polymers, the individual polymer chains of which, excluding theterminating groups, are represented by Formula (6) in the hydrochloridesalt form. This is commercially available from Avecia Inc. under thetrademark BAQUACIL

The polymeric biguanide is preferably added to the re-circulating watersystem to give a concentration thereof in the water of from 1 to 20 ppm,more preferably from 4 to 15 ppm, especially from 5 to 12 ppm, moreespecially from 6 to 10 ppm.

We have found that a combination of a polymeric biguanide (especiallyPHMB) with an adjuvant of the Formula (1) or a salt thereof providesparticularly effective control over the growth of bacteria and nuisancealgae, yeast and fungi. Furthermore, the combination of the polymericbiguanide and adjuvant gives a fast rate of kill of undesirablemicro-organisms. We have also found that the combination of adjuvant andpolymeric biguanide exhibit a high residence time in the water, therebyproviding long term protection against the growth of bacteria andnuisance algae. A long residence time is desirable because it reducesthe frequency of re-dosing with the polymeric biguanide and/or adjuvantnecessary to sustain protection in the recirculating water system.

As hereinbefore mentioned the polymeric biguanide and adjuvant may beadded sequentially in any order. However, for ease of dosing it ispreferred that they are added together as a composition comprising thepolymeric biguanide, the adjuvant and optionally a carrier. The carrier,when present, may be a solid or a liquid medium and may comprise amixture of one or more solids or liquids.

When the carrier is a solid it is preferably a solid which, whendissolved in the recirculating water system, does not have an adverseeffect upon the water, such as discoloration of the water or causingturbidity. It is especially preferred that the solid is a water solublesolid, because this avoids the formation of undesirable deposits in therecirculating water system. Solid carriers which may be used include,but are not limited to kaolin, bentonite, kieselguhr, calcium carbonate,talc, powdered magnesia, china clay or more preferably a water solubleinorganic salt, or a filler conventionally used in the preparation oftablets, such as microcrystalline cellulose, lactose and mannitol.

When the carrier is a solid the adjuvant and polymeric biguanide may besimply mixed with the carrier to provide a powder formulation which canbe added directly to the recirculating water system. Alternatively, thepowder may be encapusulated in a water-soluble capsule, for example asis commonly used for encapsulating pharmaceuticals. This has theadvantage that dosing of the powder is easily controlled, for example asingle capsule can be filled with sufficient powder to give an effectiveconcentration of the polymeric biguanide and adjuvant in therecirculating water system.

In an embodiment of the invention the polymeric biguanide and adjuvantmay be used in the form of a tablet. Suitable tablet formulationsinclude those commonly used for dispensing pharmaceuticals. The tabletsmay contain a number of components commonly used in the art of tabletformulation, for example, fillers, binders, and excipients.

When the carrier is a liquid medium, the composition is preferably asolution, suspension, emulsion, dispersion or micro-emulsion of thepolymeric biguanide and adjuvant in the liquid medium.

The liquid medium is preferably water, a water-miscible organic solventor more preferably a mixture of water and one or more water-miscibleorganic solvents.

Suitable water-miscible organic solvents include alcohols, preferablyC₁₋₆-alkanols, for example methanol, ethanol, propanol and isopropanol;diols, preferably diols having from 2 to 12 carbon atoms, for examplepentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol,pentylene glycol, hexylene glycol and thiodiglycol; oligo- andpoly-alkyleneglycols, for example diethylene glycol, triethylene glycol,dipropylene glycol, polyethylene glycol (preferably with an averageM_(n)<1000, more preferably <500) and polypropylene glycol (preferablywith an average M_(n)<1000); triols, for example glycerol and1,2,6-hexanetriol; mono-C₁₋₄-alkyl ethers of diols, preferablymono-C₁₋₄-alkyl ethers of diols having 2 to 12 carbon atoms, for example2-methoxyethanol, 2-(2-methoxyethoxy)ethanol,2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol,2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether;amides, for example N,N-dimethylformamide; cyclic amides, for exampleN-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and 2-pyrrolidone; andsulphoxides, for example, dimethylsulphoxide; carboxylic acids, forexample saturated and unsaturated aliphatic monocarboxylic ordicarboxylic acids for example methanoic, ethanoic, propanoic, butanoic,2-methylpropanoic, pentanoic, 3-methylbutanoic, 2,2-dimethylpropanoic,dodecanoic, tetradecanoic, hexadecanoic, octadecanoic, ethandioic,propanedioic, butanedioic, pentandioic, hexanedioic, heptanedioic,octanedioic, nonanedioic, and decanedioc acid, unsaturated aliphaticacid for example propenoic, propynoic, 2-methylpropenoic, trans andcis-2-butenoic, trans and cis-9-octadecanoic, trans and cis-butenoic andcis-methylbutenedioic, C₁₋₆-alkanols and C₁₋₄ saturated carboxylic acidsare particularly preferred. Especially preferred water-miscible organicsolvents include acetic acid, propanoic acid and ethanol.

If the formulation is in the form of a suspension, dispersion oremulsion, it preferably also contains a surface active agent to producea stable dispersion or to maintain the non-continuous phase uniformlydistributed throughout the continuous phase. Any surface active agentwhich does not have a significantly adverse effect on the biocidalactivity of the adjuvant and polymeric biguanide may be used. Suitablesurface active agents include emulsifiers and surfactants and mixturesthereof. The emulsifiers/surfactants may by non-ionic, anionic or amixture thereof. Suitable anionic emulsifiers and surfactants includealkylarylsulfonates (for example calcium dodecylbenzenesulfonate),alkylsulfates (for example sodium dodecylsulfate), sulfosuccinates (forexample sodium dioctylsulfosuccinate), alkylethersulfates,alkylarylethersulfates, alkylether carboxylates,alkylarylethercarboxylates, lignin sulfonates or phosphate esters.Suitable non-ionic emulsifiers and surfactants include fatty acidethoxylates, ester ethoxylates, glyceride ethoxylates (for examplecastor oil ethoxylate), alkylaryl polyglycol ethers (for examplenonylphenol ethoxylates), alcohol ethoxylates, propylene oxide-ethyleneoxide condensation products, amine ethoxylates, amide ethoxylates, amineoxides, alkyl polyglucosides, sorbitan fatty acid esters,polyoxyethylene sorbitan fatty acid esters, polyoxyethylenesorbitolesters or alcohol ethoxy carboxylates, especially those obtainable fromC₁₂₋₁₄-alcohols.

The weight ratio of the polymeric biguanide:adjuvant may vary over widelimits, but in many embodiments is from 99:1 to 1:99, preferably from4:1 to 1:4, more preferably from 1:2 to 2:1. It is especially preferredthat the weight ratio of the polymeric biguanide to adjuvant is from 1:1to 2:1.

Further improvements in the efficacy of the present method may beachieved by adding the adjuvant and polymeric biguanide to therecirculating water system in conjunction with one or more furtherantimicrobial compound(s). The addition of further antimicrobialcompound(s) to the recirculating water system can provide a broaderspectrum of antimicrobial activity and/or provide increased efficacyagainst particularly problematic algae, bacteria, yeast and/or fungipresent in the recirculating water system. Furthermore, the combinationof the adjuvant compound the polymeric biguanide and one or more furtherantimicrobial compound(s) may provide a synergistic effect.

The further antimicrobial compound(s) may possess anti-bacterial,anti-fungal, anti-algal or other antimicrobial activity. Suitablefurther anti-microbial compounds include agricultural fungicides,agricultural herbicides, algicides, sanitises, disinfectants orquaternary ammonium compounds and combinations thereof.

When the further antimicrobial compound is a sanitising agent the choiceof sanitising agent will depend upon the recirculating water system inwhich it will be used. For recreational waters, suitable sanitisingagents include for example chlorine, bromine, ozone, hydrogen peroxide,calcium hypochlorite, sodium hypochlorite, lithium hypochlorite, achlorine release agent (preferably a chlorinated isocyanurate, or achlorinated hydantoin, more preferably dichlorocyanuric acid ortrichlorocyanuric acid), a bromine release agent, a hydrogen peroxiderelease agent, an ozone release agent or water-soluble copper or silveror chelated copper salts, (e.g. copper sulphate, chelated coppersulphate). In industrial recirculating water systems where the toxicityof the sanitising agent is not so important, other sanitisers may alsobe suitable for example 2-methylisothiazolinone,5-chloro-2-methylisothiazolinone, benzisothiazolinone,2-bromo-2-nitropropane-1,3-diol, 1,2-dibromo-2,4-dicyanobutane,methylene bisthiocyanate, 2-(thiocyanomethylthio)-benzothiazole,formaldehyde and formaldehyde release agents, glutaraldehyde,dibromonitrilopropionamide and bromo-hydroxyacetophenone or mixturesthereof.

When the further antimicrobial compound is a quaternary ammoniumcompound it may be a compound with a single quaternary ammonium group ora polyquaternary ammonium compound. Examples of suitable quaternaryammonium compounds include for example,N,N-diethyl-N-dodecyl-N-benzylammonium chloride,N,N-dimethyl-N-octadecyl-N-(dimethylbenzyl)ammonium chloride,N,N-dimethyl-N,N-didecylammonium chloride,N,N-dimethyl-N,N-didodecylammonium chloride;N,N,N-trimethyl-N-tetradecylammonium chloride,N-benzyl-N,N-dimethyl-N-(C₁₂-C₁₈alkyl)ammonium chloride,N-(dichlorobenzyl)-N,-N-dimethyl-N-dodecylammonium chloride,N-hexadecylpyridinium chloride, N-hexadecylpyridinium bromide,N-hexadecyl-N,N,N-trimethylammonium bromide, N-dodecylpyridiniumchloride, N-dodecylpyridinium bisulphate,N-benzyl-N-dodecyl-N,N-bis(beta-hydroxy-ethyl)ammonium chloride,N-dodecyl-N-benzyl-N,N-dimethylammonium chloride,N-benzyl-N,N-dimethyl-N-(C₁₂-C₁₈ alkyl) ammonium chloride,N-dodecyl-N,N-dimethyl-N-ethylammonium ethylsulphate,N-dodecyl-N,N-dimethyl-N-(1-naphthylmethyl)ammonium chloride,N-hexadecyl-N,N-dimethyl-N-benzylammonium chloride orN-dodecyl-N,N-dimethyl-N-benzylammonium chloride.

In a preferred embodiment the further antimicrobial compound is apolyquaternary ammonium compound. Antimicrobial polyquaternary ammoniumcompounds which may be used include those described in U.S. Pat. Nos.3,874,870, 3,931,319, 4,027,020, 4,089,977, 4,111,679, 4,506,081,4,581,058, 4,778,813, 4,970,211, 5,051,124, 5,093,078, 5,142,002 and5,128,100 which are incorporated herein by reference thereto.

Especially preferred polyquaternary compounds comprise a repeat unit ofthe Formula (7):

wherein:

R⁴, R⁵, R⁶ and R⁷ each independently is C₁₋₆-alkyl optionallysubstituted by hydroxy;

Q²⁻ is a divalent counter ion, two monovalent counter ions or a fractionof a polyvalent counter ion sufficient to balance the cationic charge inthe repeat unit; and

a, b and t each independently is 1 to 4.

Preferably Q²⁻ is two monovalent anions selected from a halide anion anda trihalide anion, more preferably chloride or bromide.

R⁴, R⁵, R⁶ and R⁷ are preferably each independently C₁₋₄-alkyl, morepreferably methyl.

a, b and t are preferably each independently 1, 2 or 3. It is especiallypreferred that a, b and t are 2.

The polyquaternary ammonium compound with the repeat unit of Formula (7)preferably has a average molecular weight of from 1,000 to 5,000. Anespecially preferred polyquaternary ammonium compound with a repeat unitof Formula (7) ispoly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride).This polymer is commercially available under the Trademark WSCP fromBuckman Laboratories Inc.

We have found that the use of a polyquaternary ammonium (especiallypoly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride)) in addition to the polymeric biguanide and adjuvantprovides good protection against the growth of algae, especially thosecommonly found in recreational waters such as swimming pools. Thiscombination is particularly useful as a remedial treatment for algalblooms in recreational waters.

When the further antimicrobial compound is a polyquaternary ammoniumcompound it is convenient to add the adjuvant and polyquaternaryammonium compound to the recirculating water system together as aformulation. Such formulations are commercially available, for exampleBusan 20/20™ (ex Buckman Laboratories Inc.) is a formulation comprisingpoly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride) and a salt of dodecylamine.

Alternatively, the further antimicrobial compound may be added to therecirculating water system together with the adjuvant and polymericbiguanide together as a composition comprising optionally a carrier. Thecarrier, when present, may be a solid or a liquid medium. Suitable solidand liquid carriers which may be employed are as previously described.When a further antimicrobial compound is present in such a composition,the further antimicrobial compound typically comprises from 5 to 50%,and preferably from 10 to 30% by weight of the composition.

The Recirculating Water System

The invention is applicable to any industrial or recreationalrecirculating water system but is especially suitable for recreationalrecirculating water systems. Examples of industrial water systemsinclude heating and cooling systems, e.g. cooling towers and domesticcentral heating systems. Examples of recreational recirculating watersystems include swimming pools, spas and ornamental ponds. The inventionis also applicable to plumbing, pipework and other surfaces which formpart of the industrial or recreational recirculating water systems andwhich are susceptible to infection by microorganisms.

BEST MODE

A preferred embodiment comprises a method for inhibiting the growth ofor killing microorganisms, particularly algae, bacteria, yeast, and/orfungi in a recirculating water system, preferably a recreationalrecirculating water system, comprising adding to the water in eitherorder or simultaneously:

(i) dodecylamine or a salt thereof; and

(ii) a polymeric biguanide, especially PHMB;

wherein the dodecylamine adjuvant is added to the water system to give aconcentration thereof of from 0.1 to 24 ppm, preferably 0.5 to 15 ppm,more preferably 6 to 15 ppm and especially 6 to 10 ppm, and thepolymeric biguanide is added to the water system to give a concentrationthereof of from 1 to 20 ppm, preferably 5 to 12 ppm more preferably 6 to10 ppm.

The combination of components (i) and (ii) provides very effectiveprotection against the growth of microorganisms such as bacteria and“nuisance” algae, yeast and/or fungi without affecting water quality,especially water clarity.

Recirculating Water Systems

According to a second aspect of the present invention there is provideda recirculating water system comprising (i) water, an adjuvant of theFormula (1) as hereinbefore defined and a polymeric biguanide; and (ii)a means for recirculating the water; wherein the adjuvant and polymericbiguanide are dissolved in the water.

The preferred adjuvant and polymeric biguanide, their preferred amountsand the preferred water systems are as defined above in relation to thefirst aspect of the present invention.

The preferred means for recirculating the water comprises a pump.

Composition

According to a third aspect of the present invention there is provided acomposition comprising:

(i) an adjuvant of the Formula (1) as hereinbefore defined;

(ii) a polymeric biguanide; and

(iii) optionally a carrier.

The preferred adjuvants, polymeric biguanides and carriers, and weightratio of polymeric biguanide:adjuvant are as hereinbefore described inrelation to the first aspect of the present invention.

In a preferred embodiment of the invention the composition comprises:

(a) from 10 to 60 parts of a mixture comprising the compound of Formula(1) and a polymeric biguanide; and

(b) from 40 to 90 parts of a carrier wherein the parts (a) and (b) areby weight and the sum of the parts (a) and (b)=100.

Preferably the compositions comprises:

(a) from 5 to 30, more preferably 10 to 20 weight % of the compound ofFormula (1) and from 5 to 30, more preferably 10 to 20 weight % ofpolymeric biguanide; and

(b) from 90 to 60 more preferably 80 to 40 weight % of carrier.

The compositions may be used to treat recirculating water systems, forexample industrial and recreational recirculating water systems.

Kits

According to a fourth aspect of the present invention there is provideda kit for treating recirculating water comprising:

(i) an adjuvant of the Formula (1) as hereinbefore defined;

(ii) a polymeric biguanide; and

(iii) instructions for adding (i) and (ii) to a recirculating watersystem, preferably to a swimming pool, spa or ornamental pond. Theinstructions preferably comprise instructions to use (i) and (ii) forinhibiting the growth of and/or killing microorganisms such as algae,bacteria, yeast and/or fungi.

The invention is further illustrated by the following examples in whichall parts and percentages are by weight unless otherwise indicated.

EXAMPLES 1 TO 6 Preventative Laboratory Studies on Algae Pre-Amble

Preventative treatments, as the name implies, are intended to prevent anoutbreak occurring. Without adequate control measures, outbreaks canoccur in two different scenarios. In the first scenario, the organism ispresent at all times but the concentration of the organism is so lowthat it is not noticeable. If a triggering event occurs, the organismreproduces rapidly resulting in a “bloom”. Examples of triggering eventsare pH shifts, disturbance of a harbouring biofilm in the filter orplumbing, and introduction of additional but previously limitednutrients, such as nitrogen.

In the second scenario, low numbers of organisms can be introduced intoa previously non-colonized pool that having optimal growth conditions.The combination of organisms and optimal growth conditions can result ina “bloom”. The organisms can be introduced by the fill water,atmospheric dust, rainfall, or by bathing suits which have beenpreviously used in infected pools or rivers and not washed beforere-use.

In preventative laboratory treatment studies, growth conditions areoptimised to support a bloom. An experimental flask is prepared with amedium having optimised growth conditions to support a bloom, the mediumin the flask is treated with a prescribed concentration of a testformulation, and then inoculated with a low concentration of abloom-forming organism. The medium is monitored for a period of time toobserve whether the formulation is effective at preventing an algalbloom.

These studies used the most problematic organisms, i.e. field isolatedmustard algae. Any compound that shows good efficacy against suchorganisms would be expected to provide even better control against theless environmentally-robust green and black algae.

Experimental

A series of innocula of naturally occurring mustard algae was preparedby inoculating flasks of modified Jaworski's medium with un-purifiedwild algal isolates collected in the field and containing low levels ofbacteria and culturing the flasks for two weeks. The Jawaorski's mediumwas modified by the addition of 4 ppm polyhexamethylene biguanide (PHMB)(ex Avecia Inc.) to inhibit the growth of the bacteria present in thealgal isolates. The inocula were harvested by aseptic vacuum filtrationand the concentration of algal cell masses were combined (“pooled”) andredispersed in a aseptic medium to provide a concentrated pooledinoculum. The amount of inoculum used was varied to achieve an initialoptical density of 0.010 in the test flasks. The optical density wasdetermined using a Milton Roy Spec 20 spectrophotometer.

Test adjuvants and Busan 20/20™ (ex Buckman Laboratories Inc. a mixtureof dodecylamine and a polyquaternary ammonium compound (WSCP™)) wereassessed, in triplicate, for anti-algal activity and a blank control, byadding each adjuvant or known Busan 20/20™ at 0 ppm and 15 ppm toJaworski's medium (50 ml) contained in 125 ml flasks containing 6 mmborosilicate beads (50). Each flask was then inoculated with aprescribed amount of the pooled inoculum, so that the liquid in theflask had no visible green cast. The flasks (including a control orblank containing no adjuvant or Busan 20/20™ were closed withtranslucent caps and incubated at 80 F. for 10 days with 18 hours/day ofillumination by a combination of fluorescent grow lamps and standardincandescent lamps. The incubation time was 10 days. Growth was scoredby visual observation on a 0-4 scale and the results are shown in Table1 below. A score of “1” indicates that the flask is slightly green. Ascore of “2” indicates that bloom has begun. A score of “4” indicatesthat the flasks are too turbid to see through. Any score >1 isconsidered a preventative failure.

TABLE 1 Visual score - Preventive Algae Control Adjuvant PHMB AverageEx- Conc. Conc. Visual ample Adjuvant (ppm) (ppm) Score Comments 1Dodecylamine 2.5 4.0 0 no visible growth 2 Dodecylamine 5.0 4.0 0 novisible growth 3 Dodecylamine 10.0 4.0 0 no visible growth 4Dodecylamine 15.0 4.0 0 no visible growth 5 Busan 20/20 ™ 10.0 4.0 0 novisible growth 6 Busan 20/20 ™ 15.0 4.0 0 no visible growth Control None0 4.0 4.0 very heavy growth Control None 0 0 4.0 very heavy growth

The data in Table 1 clearly illustrates the effectiveness of thecombinations of PHMB and dodecylamine and PHMB and Busan 20/20™ over thePHMB, alone, at preventing the field isolated mustard algae outbreakfrom occurring.

EXAMPLES 7 TO 12 Remedial Laboratory Studies on Algae Pre-Amble

Remedial treatments are intended to reduce a bloom of algae once it hasalready occurred. During blooms the algal infestation of the system isobvious, even to the casual observer. Effective remedial treatments arethose that reduce the obvious symptoms, even if they do not result in acomplete kill of the algae. Remedial treatments are considered effectiveif they return the system to a pre-bloom state.

Remedial efficacy was evaluated in this example using field isolatedmustard algae. Any treatment showing good control of this organism isexpected to display similar efficacy against green and black algae.

Experimental

Studies were conducted in 125 ml flasks containing 6 mm borosilicateglass beads (50) and Jaworski's medium (50 ml). The flasks wereinoculated with pooled cultures of mustard algae to achieve an initialabsorbance of 0.10, as measured using a Milton Roy Spec 20Spectrophotometer. This concentration of algae in the water resulted ina noticeable green colour similar to that seen after brushing pools withmoderate blooms. The adjuvants identified in Table 2 were added atlevels of 1.25 and 2.5 ppm active ingredient. Busan 20/20™ identified inTable 3 was added at levels of 0.625, 1.25, 2.5 and 5.0 ppm. Theperformance of the adjuvants were compared to the controls with andwithout PHMB. The flasks were closed using translucent caps, illuminatedfor 8 hours using a combination of fluorescent grow lamps and standardincandescent lamps each day and incubated at 80° F. for a period of 5days. Algal growth was measured after 5 days using a Milton Roy Spec 20spectrophotometer. The higher the optical density the heavier thegrowth. Treatments that result in a terminal optical density of lessthan 0.2 display either algistatic or algicidal activity. The resultsare shown in Table 2.

TABLE 2 Remedial Algae Control Adjuvant PHMB Average Example AdjuvantConc. (ppm) Conc. (ppm) Optical Density Comments  7 Dodecylamine 2.5 4.00.12 Control (Armeen 12D ™)  8 Dodecylamine 1.25 4.0 0.08 Excellent(Armeen 12D ™) Control  9 Octadecylamine 2.5 4.0 0.08 Excellent (Armeen18 D ™) Control 10 Octadecylamine 1.25 4.0 0.16 Control (Armeen 18 D ™)11 Dimethyloctadecylamine 2.5 4.0 0.07 Excellent (Armeen DM 18D ™)Control 12 Dimethyloctadecylamine 1.25 4.0 0.12 Control (Armeen DM 18D)Control None 0 4.0 0.62 Very heavy growth Control None 0 0 0.48 Heavygrowth Footnote to Table 2: Armeen 12D, Armeen 18D and Armeen DM aretrademark names for dodecylamine, octadecylamine anddimethyloctadecylamine ex Akzo Nobel.

The data in Table 2 shows that all of the combinations of adjuvants andPHMB were successful at significantly reducing the growth of the fieldisolated mustard algae and much more effective than the PHMB by itself.Also, there was no significant difference in the performance of thestraight chained octadecylamine and dimethyloctadecylamine at 2.5 ppm.

EXAMPLE 13 Effect of an Additional Polyquaternary Ammonium Compound onthe Control of Algal Growth

The experiments described in Examples 7 to 9 were repeated except thatin place of the dodecylamine Busan 20/20™ (a mixture of dodecylamine anda polyquaternary ammonium compound available under the trademark WSCP exBuckman Laboratories Inc.) was used. The results are shown in Table 3.

TABLE 3 Remedial Algae Control PHMB Average Conc. Conc. Optical ExampleAdjuvant (ppm) (ppm) Density Comments 13 Busan 0.625 4.0 0.32 Moderategrowth 20/20 ™ 14 Busan 1.25 4.0 0.20 Slight growth 20/20 ™ 15 Busan 2.54.0 0.16 Control 20/20 ™ 16 Busan 5.0 4.0 0.12 Control 20/20 ™ ControlNone 0 4.0 0.81 Very heavy growth Control None 0 0 0.51 Heavy growth

The data in Table 3 shows that at concentrations of Busan 20/20™ greaterthan or equal to 1.25 ppm in combination with PHMB gave a significantimprovement over PHMB alone.

EXAMPLE 17 Effect of Adjuvant on Water Clarity

When treating recreational waters such as swimming pools or spas it ishighly desirable to add an agent to the water which can be dosed in oneapplication or will accumulate over time and will not adversely effectthe water quality, for example clarity, colour, foaminess, orobjectionable odour or taste. If swimming pool water is not clear itcould present a hazard to swimmers who may not be able to see the pool'ssides or bottom.

Experimental

Six 10 gallon fish aquariums equipped with a heater and a recirculatingpump (to simulate a swimming pool environment) were filled withsimulated swimming pool water containing polyhexamethylene biguanide(PHMB) comprising:

Sodium bicarbonate (total alkalinity) 80-150 ppm Calcium chloride(hardness) 180-275 ppm Hydrogen peroxide 25-30 ppm Polyhexamethylenebiguanide (PHMB) 6-12 ppm

To these tanks was added the adjuvant shown in Table 4. The pH of thetanks was maintained between 7.2 and 7.8 and the water temperature wasmaintained at 70±3° F. After the chemical additions the water wascirculated for 24 hours. The water in each tank was then visuallyinspected and tested for turbidity using a Hach Turbidimeter. Theresults are shown in Table 4.

TABLE 4 Effect of Dodecylamine and Tetradecylamine on Water ClarityAdjuvant Concentration Turbidity Visual Tank Adjuvant (ppm) (NTU)Observations 1 Control 0 2.3 Clear 2 Dodecylamine 2.5 2.7 Clear 3Dodecylamine 5.0 1.8 Clear 4 Dodecylamine 10.0 2.5 Clear 5Tetradecylamine 5.0 10.1 Cloudy 6 Tetradecylamine 10.0 19.0 Cloudy

The results in Table 4 clearly indicate that the dodecylamine had noeffect on water clarity whereas tetradecylamine resulted in waterturbidity.

What is claimed is:
 1. A method for inhibiting the growth of or killingalgae, bacteria, yeast, and/or fungi in a recirculating water systemcomprising adding to the water, (A) a polymeric biguanide, (B)dodecylamine or salt thereof, and (C) a polyquaternary ammonium compoundcomprising a repeat unit of the formula (7):

wherein: R⁴, R⁵, R⁶ and R⁷ each independently is C₁₋₆-alkyl optionallysubstituted by hydroxy; Q²⁻ is a divalent counter ion, two monovalentcounter ions or a fraction of a polyvalent counter ion sufficient tobalance the cationic charge in the repeat unit; and a, b and t eachindependently is 1 to 4 in an amount effective in inhibiting the growthof or killing said algae, bacteria, and/or fungi without affecting waterclarity.
 2. A method according to claim 1 wherein the dodecylamine orsalt thereof is added to the recirculating water system to give aconcentration thereof in the range 0.1 to 30 ppm.
 3. A method accordingclaim 1 wherein the polymeric biguanide contains at least two biguanideunits of Formula (2):

linked by a bridging group which contains at least one methylene group.4. A method according to claim 1 wherein the polymeric biguanide is amixture of polymer chains in which the individual polymer chains,excluding the terminating groups, are of the Formula (6) or a saltthereof:

wherein n is from 4 to
 40. 5. A method according to claim 1 wherein thepolymeric biguanide is in the hydrochloride salt form.
 6. A methodaccording to claim 1 wherein the polymeric biguanide is added to there-circulating water system to give a concentration thereof in the waterof from 1 to 20 ppm.
 7. A method according to claim 1 wherein thedodecylamine or salt thereof and polyquaternary ammonium compound areadded to the recirculating water system together as a formulation.
 8. Amethod according to claim 1, wherein the recirculating water system isselected from swimming pool systems, spa systems, heating systems,cooling systems, cooling towers, domestic central heating systems, andornamental ponds.
 9. The method of claim 1 wherein the polyquaternaryammonium compound ispoly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylene-dichloride.10. The method for inhibiting the growth of or killing algae, yeastand/or fungi in a recirculating water system without affecting waterclarity comprising adding to the water (A) polyhexamethylene biguanidehydrochloride salt PHMB; (B) dodecylamine or salt thereof; and (C)poly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride; wherein the dodecylamine or salt thereof is added to thewater system to give a concentration thereof of from 0.1 to 24 ppm andthe PHMB is added to the water system to give a concentration thereof offrom 1 to 20 ppm.